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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.bhp.com.au!mel.dit.csiro.au!munnari.OZ.AU!news.ecn.uoknor.edu!news.cis.okstate.edu!news.ksu.ksu.edu!news.physics.uiowa.edu!math.ohio-state.edu!howland.reston.ans.net!newsfeed.internetmci.com!netnews.nwnet.net!nwnet.net!not-for-mail From: aad@nwnet.net (Anthony D'Atri) Newsgroups: comp.unix.bsd.bsdi.misc,comp.periphs.scsi,comp.arch.storage Subject: SCSI disk geometries: weird probe defaults are faster than custom! Date: 3 Jan 1996 15:06:22 -0800 Organization: NorthWestNet, Bellevue, WA Lines: 18 Message-ID: <4cf25e$m82@olympus.nwnet.net> Reply-To: aad@nwnet.net NNTP-Posting-Host: olympus.nwnet.net Xref: euryale.cc.adfa.oz.au comp.unix.bsd.bsdi.misc:1916 comp.periphs.scsi:44388 comp.arch.storage:7675 (Intel P90 machine running BSDI 2.01) I discovered that when I newfs'd C partitions, dumpfs complained about there not being room for the rotation tables. This led me to discover that when one has disksetup [P]robe a disk, it defines the geometry to be fairly bizarre. For example, it reports a ~2G Seagate ST32250N as having 2048 sectors/track, 1 head, and 2048 cylinders. When I newfs a C partition on this disk with this strange geometry, iozone gives me 32.18/58.25 seconds to write/read a 100M file. When I newfs it with a carefully constructed more normal-looking geometry (126 sectors/track, 11 heads, 3026 cylinders) iozone is much slower, taking 51.3/103.15 seconds to write/read a 100M file on a newly newfs'd filesytem. Comments? Any suggestions on whether I should go with the hand-built geometries or the strange Probed ones? Is it the case that iozone does not reflect a normal random-access read/write usage pattern, and that I should ignore the above results? I'm building a news machine here, and want to tune it as best I can.